The technical field relates generally to radioactive sourcewires for treatment of diseases, and, more particularly, to a flexible sourcewire for use in radiation therapy after an angioplasty procedure in order to minimize the occurrence of restenosis.
During or after the performance of a percutaneous transluminal angioplasty procedure to relieve a constriction within a patient""s vessel, it has been found beneficial to irradiate the site of the constriction to prevent reclosure or restenosis due to smooth muscle cell proliferation. Typically, a catheter having a blind lumen extending to a distal end thereof is advanced to the treatment site and a sourcewire having a radioactive tip is advanced to the treatment zone of the catheter adjacent the treatment site within the vessel. This is typically accomplished by connecting a proximal end of a catheter to a mechanism for advancing the sourcewire, such as an afterloader, and operating the afterloader to advance the sourcewire to the treatment site.
Commonly, in afterloaders, the sourcewire is substantially wound about a reel or spool with only the distal end, that end containing the radioactive source, left in a straight or uncoiled position. The radioactive source is typically housed within a shielded container provided on the afterloader. In operating the afterloader, the sourcewire is unraveled off the reel and advanced through the catheter down the various narrow or tortuous pathways to reach the arteries and, in particular, the remote coronary arteries. Sourcewires may be repeatedly used over again until such time as the radioactive level of the radioactive source is of no further beneficial use.
During the repeated cycling of the sourcewire about the reel and through the catheter to reach the coronary arteries, the sourcewire is subjected to various stresses and strains along its length thereof. This may pose problems in particular sourcewire constructions which can result in cracking, buckling or kinking at various positions along the sourcewire. In one known sourcewire construction, the sourcewires are formed by having a thin walled tube with a substantially full length backbone wire affixed therein. The backbone wire terminates short of the distal end of the tube to define a cavity for receipt of a radioactive source or sources therein. The backbone wire construction of the radioactive sourcewire provides the advantage of allowing a relatively long treatment zone to be provided by the tube defining the cavity at a distal end thereof. Alternatively, sourcewires formed from an entirely solid wire having a drilled distal end for receipt of a radioactive core are known. The solid wire construction is less prone to damage from repeated cycling. However, when constructing sourcewires of relatively small diameters, i.e. generally less than 0.014 of an inch, it becomes difficult to drill a cavity into the solid wire of sufficient length to accommodate the desired longer radioactive sources.
Thus, there exists a need for a radioactive sourcewire combining the strength and flexibility of a substantially solid wire along the predominant length thereof as well as having a tubular construction at a distal most end to accommodate varying lengths of radioactive sources.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the radioactive sourcewire and method for forming a radioactive sourcewire of the present invention. The present method for forming a radioactive sourcewire includes providing a generally elongated thick walled tubular member and drilling an enlarged cavity in the distal end of the tubular member. The cavity is of sufficient length to retain a radioactive source. During drilling of the cavity, material removed from the tubular member to form the cavity is preferably allowed to flow from the cavity and into a bore of the elongated tubular member to thereby form a plug and to seal the cavity from the bore. A radioactive source may then be inserted into the cavity either in a radioactive state, in which case the source is preferably coated with a neutron permeable material, or an inert state. The distal end of the tubular member is then welded or otherwise sealed shut to seal the radioactive source within the cavity. Finally, the proximal end of the elongated tubular member may also be welded or otherwise sealed shut.
The disclosed sourcewire generally includes an elongated tubular member having a substantially elongated bore of a first diameter and an enlarged cavity formed in the distal end of the tubular member having a diameter greater than that of the first diameter. A radioactive source is positioned within the cavity and the distal end of the elongated tubular member is sealed, preferably by being welded shut, or by other methods. Preferably, the sourcewire additionally includes a plug between the bore of the elongated tubular member and the enlarged cavity. Further, the plug may preferably be formed of material removed from the elongated member to form the enlarged cavity. A proximal end of the radioactive sourcewire is welded shut.
The above description and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings and appended claims.